1. Field of the Invention
The present invention relates to a measurement technology using electromagnetic waves. The invention particularly relates to an interface detection apparatus and method for detecting the hidden interface of materials employing the near-field region (the Fresnel region) antenna technology.
2. Description of the Related Art
There is a case where a hidden interface such as an interface between air and liquid contained in an opaque glass or an opaque plastic container must be detected externally. Since there is no earlier method of detecting the internal liquid level if, in particular, a container is opaque or has an opaque sheet such as paper attached on the surface, the position thereof has to be found through visual observation from the inlet disposed above, and necessary operations for detecting precisely the hidden liquid level must then be carried out. A hidden interface detection apparatus, which detects the hidden interface of materials externally from an opaque container without making contact with inner hidden materials contained in them, has been in demand in order to automate those operations. However, at present, no appropriate hidden interface detection apparatus and method has been known.